By Ushanandini Mohanraj
Have you ever wondered, “Why the emergence of infectious diseases have doubled over time?”, Why mankind is crippled by the new viruses and parasites which had remained dormant all these years? Most people argue that these infectious agents are getting smarter. I would definitely agree with this as there has always been survival of the fittest. However this might not be the sole case!
One of the most arguable reasons for such emergence is the loss of biodiversity. How? Animals and plants have always acted as a buffer between people and disease-causing pathogens. But due to loss of biodiversity and species vanishing at a faster pace, this shield has come down. Since 1970, diversity of birds, mammals, amphibians, reptiles and fish has declined by almost 30 per cent, a report by WWF stated.
The biodiversity loss and increase of disease transmission was studied by a research team led by Felicia Keesing, a biologist at Bard College. They studied spread of several diseases, including hantavirus pulmonary syndrome, a fatal disease spread by rodents. Hantavirus is a group of viruses that feed on rodents. The disease is transmitted to humans through rodent bites. If loss in biodiversity reduces species which prey on rodents, then density of hosts or carrier rodents will increase, and so will transmission of the disease.
Transmission can also occur if the number of hosts remains constant when biodiversity declines. To support this, a paper was published in 2009 in Nature about a study on schistosomiasis, a parasitic affliction among people in tropical climates. Schistosomiasis is caused by Schistosoma mansoni, a parasite which infects snails and humans. In an experimental setup, equal numbers of host snails were put in two tanks. In one tank, species of non-host snails were added to increase diversity. Both the tanks were then exposed to the parasite. It was observed that the snails in the single species tanks were 30 per cent more likely to get infected than those in the tank with diverse snails as parasite often ended in dead-end hosts.
In the ironical situation when the host species are lost in the ecosystem, chances of disease transmission reduce because pathogen declines. However, such instances are rare.
Apart from nature lovers working for saving wildlife, it’s time for the less enthusiastic ones to lend them a hand as even your life is at stake.